/*
 * Copyright (c) 2000-2010 Marc Alexander Lehmann <schmorp@schmorp.de>
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 */

#include "lzfP.h"

#define HSIZE (1 << (HLOG))

/*
 * don't play with this unless you benchmark!
 * the data format is not dependent on the hash function.
 * the hash function might seem strange, just believe me,
 * it works ;)
 */
#ifndef FRST
#define FRST(p) (((p[0]) << 8) | p[1])
#define NEXT(v, p) (((v) << 8) | p[2])
#if ULTRA_FAST
#define IDX(h) (((h >> (3 * 8 - HLOG)) - h) & (HSIZE - 1))
#elif VERY_FAST
#define IDX(h) (((h >> (3 * 8 - HLOG)) - h * 5) & (HSIZE - 1))
#else
#define IDX(h) ((((h ^ (h << 5)) >> (3 * 8 - HLOG)) - h * 5) & (HSIZE - 1))
#endif
#endif
/*
 * IDX works because it is very similar to a multiplicative hash, e.g.
 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
 * the latter is also quite fast on newer CPUs, and compresses similarly.
 *
 * the next one is also quite good, albeit slow ;)
 * (int)(cos(h & 0xffffff) * 1e6)
 */

#if 0
/* original lzv-like hash function, much worse and thus slower */
#define FRST(p) (p[0] << 5) ^ p[1]
#define NEXT(v, p) ((v) << 5) ^ p[2]
#define IDX(h) ((h) & (HSIZE - 1))
#endif

#define MAX_LIT (1 << 5)
#define MAX_OFF (1 << 13)
#define MAX_REF ((1 << 8) + (1 << 3))

#if __GNUC__ >= 3
#define expect(expr, value) __builtin_expect((expr), (value))
#define inline inline
#else
#define expect(expr, value) (expr)
#define inline static
#endif

#define expect_false(expr) expect((expr) != 0, 0)
#define expect_true(expr) expect((expr) != 0, 1)

/*
 * compressed format
 *
 * 000LLLLL <L+1>    ; literal, L+1=1..33 octets
 * LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset
 * 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset
 *
 */

unsigned int lzf_compress(const void *const in_data, unsigned int in_len, void *out_data,
                          unsigned int out_len
#if LZF_STATE_ARG
                          ,
                          LZF_STATE htab
#endif
) {
#if !LZF_STATE_ARG
    LZF_STATE htab;
#endif
    const u8 *ip = (const u8 *)in_data;
    u8 *op = (u8 *)out_data;
    const u8 *in_end = ip + in_len;
    u8 *out_end = op + out_len;
    const u8 *ref;

    /* off requires a type wide enough to hold a general pointer difference.
     * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
     * works for differences within a single object). We also assume that no
     * no bit pattern traps. Since the only platform that is both non-POSIX
     * and fails to support both assumptions is windows 64 bit, we make a
     * special workaround for it.
     */
#if defined(WIN32) && defined(_M_X64)
    unsigned _int64 off; /* workaround for missing POSIX compliance */
#else
    unsigned long off;
#endif
    unsigned int hval;
    int lit;

    if(!in_len || !out_len)
        return 0;

#if INIT_HTAB
    memset(htab, 0, sizeof(htab));
#endif

    lit = 0;
    op++; /* start run */

    hval = FRST(ip);
    while(ip < in_end - 2) {
        LZF_HSLOT *hslot;

        hval = NEXT(hval, ip);
        hslot = htab + IDX(hval);
        ref = *hslot + LZF_HSLOT_BIAS;
        *hslot = ip - LZF_HSLOT_BIAS;

        if(1
#if INIT_HTAB
           && ref < ip /* the next test will actually take care of this, but this is faster */
#endif
           && (off = ip - ref - 1) < MAX_OFF && ref > (u8 *)in_data && ref[2] == ip[2]
#if STRICT_ALIGN
           && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
#else
           && *(u16 *)ref == *(u16 *)ip
#endif
        ) {
            /* match found at *ref++ */
            unsigned int len = 2;
            unsigned int maxlen = in_end - ip - len;
            maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;

            if(expect_false(op + 3 + 1 >= out_end)) /* first a faster conservative test */
                if(op - !lit + 3 + 1 >= out_end)    /* second the exact but rare test */
                    return 0;

            op[-lit - 1] = lit - 1; /* stop run */
            op -= !lit;             /* undo run if length is zero */

            for(;;) {
                if(expect_true(maxlen > 16)) {
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;

                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;

                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;

                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                    len++;
                    if(ref[len] != ip[len])
                        break;
                }

                do
                    len++;
                while(len < maxlen && ref[len] == ip[len]);

                break;
            }

            len -= 2; /* len is now #octets - 1 */
            ip++;

            if(len < 7) {
                *op++ = (off >> 8) + (len << 5);
            } else {
                *op++ = (off >> 8) + (7 << 5);
                *op++ = len - 7;
            }

            *op++ = off;

            lit = 0;
            op++; /* start run */

            ip += len + 1;

            if(expect_false(ip >= in_end - 2))
                break;

#if ULTRA_FAST || VERY_FAST
            --ip;
#if VERY_FAST && !ULTRA_FAST
            --ip;
#endif
            hval = FRST(ip);

            hval = NEXT(hval, ip);
            htab[IDX(hval)] = ip - LZF_HSLOT_BIAS;
            ip++;

#if VERY_FAST && !ULTRA_FAST
            hval = NEXT(hval, ip);
            htab[IDX(hval)] = ip - LZF_HSLOT_BIAS;
            ip++;
#endif
#else
            ip -= len + 1;

            do {
                hval = NEXT(hval, ip);
                htab[IDX(hval)] = ip - LZF_HSLOT_BIAS;
                ip++;
            } while(len--);
#endif
        } else {
            /* one more literal byte we must copy */
            if(expect_false(op >= out_end))
                return 0;

            lit++;
            *op++ = *ip++;

            if(expect_false(lit == MAX_LIT)) {
                op[-lit - 1] = lit - 1; /* stop run */
                lit = 0;
                op++; /* start run */
            }
        }
    }

    if(op + 3 > out_end) /* at most 3 bytes can be missing here */
        return 0;

    while(ip < in_end) {
        lit++;
        *op++ = *ip++;

        if(expect_false(lit == MAX_LIT)) {
            op[-lit - 1] = lit - 1; /* stop run */
            lit = 0;
            op++; /* start run */
        }
    }

    op[-lit - 1] = lit - 1; /* end run */
    op -= !lit;             /* undo run if length is zero */

    return op - (u8 *)out_data;
}
